It is of limited specific use depending on context. That said though, it isn't unusual for a child whose iq scores extremely high, to be equally highly adept in picking up information, manipulating it, and using it in context. So, often, those who score 'high' in iq tests will also be the ones that teachers, parents, and bob walking past in the street think (and comment) 'gosh, she/ he's bright, eh?'
It isn't hard and fast - there are children who score highly but have significantly lower social skills and their comprehension and knowledge aren't as accessible to teachers, parents, and other folk. And there are children who struggle to maintain focus, but when they can, can produce outstanding complex understanding and display a much greater depth of knowledge than their peer group...
Iq is interesting. For at least one of my kids, her iq score has meant that she is taken seriously as a student in school. She would have been one of the children written written off, housed in an institution, and left to rot if she had been born sooner. (She has cerebral palsy. Passers by tend to pat her on the head, 'aw bless' and write her off as a tragedy.) she has a higher iq than her paediatrician, taught herself to read before she could talk, and intends to study law.
Interestingly, we only had her tested (at five) because we were trying emigrate, and no one wants a kid with a label like cp. She was deemed to be a likely 'burden on the state' for the country we were moving to, and our immigration was likely to be turned down as a result. So, we were told we had to prove she didn't have a learning disability. Whether mn posters like iq tests or not, governments officials do (I'm not making any comments about the efficacy). So, we had to fork out for a full clinical psych/ ed psych assessment. The results of this (of course the immigration had never met my child, and so were solely relying on the scores on paper) meant that we were able to move.
I do understand that high iq is often dismissed as meaningless - but for dd1 it means she is overturning societal expectations of people with disabilities, and actually being given the opportunity of an education in line with her ability, not her disability. So, you know what, it works for me as a fairly blunt tool.